#include<stdio.h>
int main()
{
    int n;
    long long factorial = 1;
    scanf("%d", &n);
    if (n < 0)
    {
        printf("Invalid input");
    }
    else
    {
        for (int i = 1; i <= n; i++){
            factorial *= i;
        }
        printf("lld", factorial);
    }
    return 0;
}